The two objectives of this Core are: 1) to understand how indoor and outdoor air pollution contributes to human respiratory diseases (including asthma), and 2) how host factors (i.e., sensitivity) influence the pathogenic process. This Core studies large populations epidemiologically and smaller groups in experimental chamber studies. Thus, it is involved in looking at both acute and chronic respiratory effects in multiple studies. This Core works closely with the Exposure Assessment (EA) Core and the Cores involved in study design and biostatistics. There are several ongoing research projects in which this Core works: There is a major longitudinal population study of chronic respiratory effects of air pollution in children in different communities in Southern California (supported by CARB). An additional grant (supported by EPA, NIEHS, NHLBI) is now evaluating dietary factors and some genetic polymorphisms. There are two ongoing experimental chamber studies of cardio-pulmonary responses of health and asthmatic subjects to particulates using an ambient particle concentrator (supported by EPA and HEI).